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  • Heroin
    • Mode of action
      • mimics endorphins (body's natural opiates)
      • Occupies and blocks pain receptor sites
      • Stimulates dopamine reward cycle
        • blocks GABA (inhibits dopamine) at the synapse
          • causes dopamine to flood
    • Short term effects
      • Rapidly produces euphoric feeling
        • 7 seconds after injection
      • Analgesic effect
        • Calm
        • aches/pains disappear
      • depresses body activities
        • slower, shallower breathing
        • lower heart rate
          • very relaxed and sleepy
      • peripheral blood vessels dilate
        • flushed, warm, and sweaty
      • want to vomit
        • depresses vomiting centre in brain
          • nausea decreases as effects build up
      • underactive digestive system
        • permanent constipation
      • very low sex drive
    • Tolerance
      • develops very quickly
      • Griffiths, Bigelow, & Henningfield 1980 - can increase up to tenfold in 3 - 4 months
      • body believes normal level of dopamine is higher due to chemical changes in the brain
        • need more dopamine to feel normal
      • regular user takes a high enough dose to kill a non-user
    • Physical dependence
      • develops very quickly
      • brain rapidly becomes used to heroin stimulating reward cycle and flood receptor sites
      • increases as tolerance does
      • established as user takes fixes to avoid increasingly severe withdrawal symptoms
      • 1 fix can produce withdrawal symptoms if more isn't taken within 12 hours
      • as physical dependence gets worse, psychologically the prospect of coping without the drug feels worse
    • Psychological dependence
      • addict ceases to be concerned about maintaining contact with family/friends
      • focus of life becomes finding next fix
      • when no in immediate effects of a fix, may feel agitated, restless, confused, and paranoid
        • can only be relieved by taking more heroin or having treatment
    • Withdrawal
      • symptoms start 6 - 12 hours after last fix
      • failure to take a fix makes symptoms increase
      • symptoms peak after 26 - 72 hours
      • most symptoms are over within a week
      • become agitated, restless, and aggressive
      • alternate between feeling hot and cold
      • chicken skin
      • short jerky breathing
      • sleep for up to 12 hours
        • wake to cramps, vomiting, diarrhoea, shaking, sweating, and twitching limbs
      • gradually subsides


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